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  4. Characterization and Control of a Pneumatic Motor for MR-conditional Robotic Applications

Characterization and Control of a Pneumatic Motor for MR-conditional Robotic Applications

AUTHORS

Chen Yue , Godage Isuru S , Tse Zion Tsz Ho , Webster Robert J , Barth Eric J . IEEE/ASME transactions on mechatronics : a joint publication of the IEEE Industrial Electronics Society and the ASME Dynamic Systems and Control Division. 2017 11 1; 22(6). 2780-2789

ABSTRACT

Magnetic Resonance (MR) guided interventional robots have recently been developed for a variety of surgeries, such as biopsy, ablation, and brachytherapy. The actuators and encoders that power and track such robots must be MR-conditional. In this paper, we propose an MR-conditional pneumatic motor with an integrated and custom-built fiber-optical encoder that provides powerful and accurate actuation. The motor is coupled with a modular plastic gearbox that provides a variety of gear ratio options so that the motor can be adapted to application requirements. With a 100:1 gear reduction at 0.55 MPa, the motor achieves 460 mNm stall torque and 370 rpm no-load speed, which leads to the peak output power of 6W. The motor has the bandwidth of approximately 1.1 Hz and 3.5 Hz when connected to 8 m and 0.2 m air hoses, respectively. The motor was tested in a 3T MRI scanner. No image artifact was observed and maximum signal to noise ratio (SNR) variation was less than 5%. Different from most of the existing MR-conditional pneumatic actuators, the proposed motor shape is more like the traditional electric motors, which offers more flexibility in the MR-conditional robot design.

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